scholarly journals Effect of compaction pressure on consolidation behaviour of unsaturated silty soil

2004 ◽  
Vol 41 (3) ◽  
pp. 540-550 ◽  
Author(s):  
A R Estabragh ◽  
A A Javadi ◽  
J C Boot
Keyword(s):  
Unsaturated Soil ◽  
Yield Curve ◽  
Compaction Pressure ◽  
Triaxial Tests ◽  
Silty Soil ◽  
Triaxial Apparatus ◽  
Soil Fabric ◽  
Isotropic Consolidation ◽  
The Difference ◽  
Soil Behaviour

The effect of compaction pressure on subsequent soil behaviour during isotropic consolidation has been investigated by conducting controlled-suction triaxial tests on samples of an unsaturated compacted silty soil. A comprehensive set of laboratory experiments was carried out in a double-walled triaxial apparatus on samples of unsaturated soil that were prepared using two different compaction pressures. The axis translation technique was used for creating the desired suctions in the samples. In the experiments, the soil samples were subjected to isotropic consolidation under constant suctions. The results show that different compaction pressures produce different fabrics in a soil and therefore affect the behaviour of the soil. The results also show that the value of yield stress and the location of the loading–collapse (LC) yield curve are functions of soil fabric. Furthermore, it is shown that the slopes of normal consolidation lines for densely and loosely compacted samples differ in unsaturated conditions but are the same in saturated soils. A comparison is made between the behaviour of the dense and loose samples, and the difference in the behaviour is explained.Key words: suction, unsaturated soil, compaction, consolidation, soil fabric.

Stress–strain behaviour of unsaturated soil in true triaxial tests

2002 ◽  
Vol 39 (3) ◽  
pp. 608-619 ◽  
Author(s):  
Hajime Matsuoka ◽  
De'an Sun ◽  
Akiteru Kogane ◽  
Nobuhiko Fukuzawa ◽  
Wataru Ichihara
Keyword(s):  
Unsaturated Soil ◽  
Failure Criterion ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Triaxial Tests ◽  
Principal Stresses ◽  
True Triaxial ◽  
Triaxial Apparatus ◽  
True Triaxial Apparatus ◽  
True Triaxial Tests

A suction-controlled true triaxial apparatus for unsaturated soil was developed from the existing true triaxial apparatus for sand by attaching a device to supply matric suction to specimens. Using the developed apparatus, true triaxial tests (σ1 [Formula: see text] σ2 [Formula: see text] σ3; where σ1, σ2, and σ3 are the three different principal stresses) on an unsaturated silty soil were carried out under constant suction using the negative pore-water pressure method (s = –uw > 0; ua = 0) for applying the matric suction, s (s = ua – uw; where ua is the pore-air pressure and uw is the pore-water pressure). It was found that the true triaxial test results under three different principal stresses are uniquely arranged on the "extended spatially mobilized plane (extended SMP)" for frictional and cohesive materials that is modified from the original SMP for frictional materials by introducing "a bonding stress, σ0 (= c·cotϕ, where c is cohesion and ϕ is the internal friction angle)." It was also found that the shear strengths of the unsaturated silty clay obtained by the true triaxial apparatus nearly agree with the extended SMP failure criterion (Î1Î2/Î3 = constant, where Î1, Î2, and Î3 are the first, second, and third invariants of the translated stress tensor). The measured stress-strain-strength behaviour of the unsaturated soil in three-dimensional (3D) stresses can be well simulated by an elastoplastic model with the transformed stress based on the extended SMP criterion and a special hardening parameter.Key words: failure criterion, shear strength, special shear test, suction, stress path, unsaturated soil.

A Rational Approach to Consolidated Undrained Triaxial Testing

1986 ◽  
Vol 2 (1) ◽  
pp. 167-175
Author(s):  
A. M. Coatsworth
Keyword(s):  
Rational Approach ◽  
Triaxial Tests ◽  
Triaxial Testing ◽  
Natural Soil ◽  
Commercial Practice ◽  
Site Investigations ◽  
Anisotropic Consolidation ◽  
Isotropic Consolidation ◽  
Undrained Strength ◽  
Soil Behaviour

AbstractBecause of sampling disturbance the results of unconsolidated undrained triaxial tests often show a considerable scatter and seriously underestimate the undrained strength of a natural soil.Therefore, consolidated undrained triaxial testing is sometimes used, the fundamentally based methods being Bjerrum's, in which specimens are anisotropically consolidated to the field effective stresses, and the SHANSEP method, in which specimens are consolidated to much higher stresses, allowed to swell if the soil is overconsolidated in situ, and the results then normalised. The relative merits of these two approaches depend on the type of soil.In commercial practice, however, most consolidated undrained triaxial testing is carried out on a purely empirical basis, in part because both the Bjerrum and SHANSEP methods require anisotropic consolidation procedures which are not commonly available. Approximations to actual soil behaviour can be used to devise a Modified SHANSEP method, which utilises conventional isotropic consolidation.Two site investigations are cited as examples of the use of the method, and in both cases the derived undrained strengths were higher than those from unconsolidated undrained testing.

Inclusion of specific water volume within an elasto-plastic model for unsaturated soil

1996 ◽  
Vol 33 (1) ◽  
pp. 42-57 ◽  
Author(s):  
S J Wheeler
Keyword(s):  
Water Content ◽  
Unsaturated Soil ◽  
Critical State ◽  
Constitutive Models ◽  
Degree Of Saturation ◽  
Triaxial Tests ◽  
Water Volume ◽  
Plastic Model ◽  
Elasto Plasticity ◽  
Soil Behaviour

Existing elasto-plastic critical state constitutive models for unsaturated soil provide no information on the variation of water content or degree of saturation. These models cannot therefore, for example, be used to predict unsaturated soil behaviour during undrained loading, when the variation of suction is determined by the requirement that water content remains constant. This problem has been tackled by extending an existing elasto-plastic model to include relationships describing the variation of specific water volume (the volume of water and solids in an element of soil containing unit volume of solids). The proposed form of the variation of specific water volume was based on consideration of the soil fabric, resulting in a coupled form of elasto-plastic behaviour. Predictions from the elasto-plastic model showed good agreement with the experimental results from suction-controlled triaxial tests on unsaturated samples of compacted speswhite kaolin. Normal compression lines for specific water volume at different values of suction were well predicted, as was the variation of specific water volume during wetting. Critical state values of specific water volume were slightly underestimated, but test paths for both drained and undrained shearing were predicted with reasonable success. Key words: compacted clays, constitutive model, critical state, elasto-plasticity, triaxial tests, unsaturated.

scholarly journals Recommended Procedures to Assess Critical State Locus from Triaxial Tests in Cohesionless Remoulded Samples

Geotechnics ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 95-127
Author(s):  
António Viana da Fonseca ◽  
Diana Cordeiro ◽  
Fausto Molina-Gómez
Keyword(s):  
Critical State ◽  
Review Paper ◽  
State Theory ◽  
Soil Freezing ◽  
Triaxial Tests ◽  
Cohesionless Soils ◽  
Saturation Condition ◽  
Testing Procedures ◽  
Laboratory Procedures ◽  
Soil Behaviour

The critical state theory is a robust conceptual framework for the characterisation of soil behaviour. In the laboratory, triaxial tests are used to assess the critical state locus. In the last decades, the equipment and testing procedures for soil characterisation, within the critical state framework, have advanced to obtain accurate and reliable results. This review paper summarises and describes a series of recommended laboratory procedures to assess the critical state locus in cohesionless soils. For this purpose, results obtained in the laboratory from different cohesionless soils and triaxial equipment configurations are compiled, analysed and discussed in detail. The procedures presented in this paper reinforce the use of triaxial cells with lubricated end platens and an embedded connection piston into the top-cap, together with the verification of the full saturation condition and the measurement end-of-test water content—preferable using the soil freezing technique. The experimental evidence and comparison between equipment configurations provide relevant insights about the laboratory procedures for obtaining a reliable characterisation of the critical state locus of cohesionless geomaterials. All the procedures recommended herein can be easily implemented in academic and commercial geotechnical laboratories.

Effects of Stress Path and Stress History on the Stiffness of Reconstituted London Clay

1986 ◽  
Vol 2 (1) ◽  
pp. 139-144 ◽  
Author(s):  
J. H. Atkinson ◽  
J. S. Evans ◽  
D. Richardson
Keyword(s):  
Stress Path ◽  
Triaxial Tests ◽  
Soil Parameters ◽  
Stress History ◽  
Strain Behaviour ◽  
Reconstituted Soil ◽  
Path Dependent ◽  
London Clay ◽  
Soil Behaviour

AbstractSoil behaviour is stress history dependent and stress path dependent and soil parameters, particularly those for stress-strain behaviour, measured in conventional triaxial tests may not represent the behaviour of soil in many civil engineering works.To obtain more realistic parameters it may be necessary to conduct laboratory tests which more closely represent in situ conditions before and during construction.The paper describes equipment developed at The City University to carry out stress path tests simply and economically. A series of CU triaxial tests and stress path tests on reconstituted soil illustrate the dependence of measured soil parameters on stress history and stress path.

Consolidation thermique par chaleur d'un sol non saturé

1991 ◽  
Vol 28 (1) ◽  
pp. 42-50 ◽  
Author(s):  
C. Saix
Keyword(s):  
Unsaturated Soil ◽  
Constitutive Law ◽  
Saturated Soils ◽  
Soil Consolidation ◽  
Thermal Compression ◽  
Triaxial Apparatus ◽  
Thermal Consolidation ◽  
Sol Non Saturé ◽  
Temperature Parameter ◽  
Definition Of

The thermal consolidation by heating of an unsaturated silty soil is studied by means of six tests performed in a thermal triaxial apparatus. The results show the importance of the temperature parameter and a clear similarity with the classical consolidation tests on saturated soils. A constitutive law is proposed for the thermal consolidation by heat that allows the definition of indices of thermal compression. This law is used to calculate the displacements in an unsaturated fill for heat storing. Key words: unsaturated soil, consolidation, heat, triaxial, modelling. [Translated by the Journal]

Effects of fines on liquefaction behaviour in well-graded materials

2017 ◽  
Vol 54 (10) ◽  
pp. 1460-1471 ◽  
Author(s):  
Katherine A. Kwa ◽  
David W. Airey
Keyword(s):  
Critical State ◽  
Soil Mechanics ◽  
State Parameter ◽  
Triaxial Tests ◽  
Particle Sizes ◽  
Graded Materials ◽  
Fines Content ◽  
Cyclic Resistance ◽  
Wide Range ◽  
Soil Behaviour

This study uses a critical state soil mechanics perspective to understand the mechanics behind the liquefaction of metallic ores during transport by ship. These metallic ores are transported at relatively low densities and have variable gradings containing a wide range of particle sizes and fines contents. The effect of the fines content on the location of the critical state line (CSL) and the cyclic liquefaction behaviour of well-graded materials was investigated by performing saturated, standard drained and undrained monotonic and compression-only cyclic triaxial tests. Samples were prepared at four different gradings containing particle sizes from 9.5 mm to 2 μm with fines (<75 μm) contents of 18%, 28%, 40%, and 60%. In the e versus log[Formula: see text] plane, where e is void ratio and [Formula: see text] is mean effective stress, the CSLs shifted upwards approximately parallel to one another as the fines content was increased. Transitional soil behaviour was observed in samples containing 28%, 40%, and 60% fines. A sample’s cyclic resistance to liquefaction depended on a combination of its density and state parameter, which were both related to the fines content. Samples with the same densities were more resistant to cyclic failure if they contained higher fines contents. The state parameter provided a useful prediction for general behavioural trends of all fines contents studied.

scholarly journals Magnetic measurement system of sandy gravel specimens shape during tests in a large triaxial apparatus

2019 ◽  
Vol 92 ◽  
pp. 02004
Author(s):  
Roberta Ventini ◽  
Alessandro Flora ◽  
Stefania Lirer ◽  
Claudio Mancuso
Keyword(s):  
Relative Humidity ◽  
Mechanical Response ◽  
Magnetic Measurement ◽  
Triaxial Tests ◽  
Sandy Gravel ◽  
Partially Saturated ◽  
Triaxial Apparatus ◽  
Large Size ◽  
Size Of Particles ◽  
The University

As well known, rockfill behaviour is strongly influenced by both intrinsic (mineralogy and size of particles, grain shapes, soil grading etc.) and state parameters (relative density, stress state, relative humidity). To investigate their mechanical response to stresses and relative humidity (RH) loadings, a large size triaxial device (H = 410 mm, D = 200 mm) has been developed at the University of Naples Federico II (Italy), including modifications required to impose partially saturated conditions in the specimen by means of the vapour equilibrium technique. In order to evaluate local axial and radial strains and global volumetric strains in partially saturated conditions, a magnetic shape detector device has been designed and installed. The accuracy of this system has been evaluated in some isotropic compression triaxial tests on compacted sandy-gravel specimens. The experimental data clearly show the effectiveness of the magnetic system in the measurement of axial displacements while the measurement in radial direction appear to be strongly affected by the non-linearity of the complex magnetic field generated during the test and requires further checking tests.

scholarly journals Spring Deformation Gauge for Measuring Local Deformations in Triaxial Apparatus

2019 ◽  
Vol 2019 ◽  
pp. 1-9
Author(s):  
Mostafa A. Ismail ◽  
Yasser E. Ibrahim
Keyword(s):  
Accurate Determination ◽  
Cost Effective ◽  
Local Deformation ◽  
Spring Steel ◽  
Metal Strip ◽  
Triaxial Tests ◽  
Strain Gauges ◽  
Soil Stiffness ◽  
Triaxial Apparatus ◽  
Measured Deformation

Local measurement of deformations of a soil specimen has become inevitable for accurate determination of soil stiffness in triaxial tests. Although there are now many devices that can be used to perform this task, each has its own advantages and limitations that render development of new devices with better desirable features. This paper presents an innovative device called spring deformation gauge (SDG) that has many advantages over many of the existing devices and can be readily manufactured in both research and commercial laboratories. The device is based on using a highly flexible, yet very strong metal strip of spring steel secured between two stiff, stainless steel L-shaped legs; the spring strip is provided with four strain gauges. With this arrangement, local deformation of a specimen is transferred into significant bending in the metal strip and elongation or shortening of the strain gauges. In addition to being very cost effective, the SDG is characterized by the ability to control both range and resolution of measured deformation, its linear output, and a clever pinning mechanism that protects it from being damaged when it goes out of range. Success of the SDG was demonstrated in a true K0 test on carbonate sand.

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